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C rowley et al.: J ournal of AOAC International Vol. 97, No. 2, 2014 431
Evaluation of VIDAS® UP Listeria Assay (LPT) for the
Detection of Listeria in a Variety of Foods and Environmental
Surfaces: First Action 2013.10
Erin C rowley, Patrick Bird, Jonathan Flannery, M. Joseph Benzinger, Jr, Kiel Fisher, Megan Boyle,
Travis H uffman, B en Bastin, Paige Bedinghaus, W illiam Judd, T hao Hoang, James Agin, and David Goins
Q Laboratories, Inc., 1400 Harrison Ave, Cincinnati, OH 45214
Ronald L. Johnson1
bioMérieux, Inc., 595 Anglum Rd, Hazelwood, MO 63042
Collaborators: A. Bollenbacher; B. Brahmanda; R. Burkhart; J. Cannon; A. Capps; L. Cesanas; D. Davis; D. Ebbing; H. Elgaali;
B. Hand; R. Hiles; J. Hirsch; B. Howard; J. Jolly; S. Joseph; A. Kehres; K. Klemms; J. Li; B. May; M. Michels; J. Mills; S. Moore;
N. Nagassar; S. Owusu; N. Palen; L. Parker; B. Paul; B. Perry; J. Pickett, N. Rogman; G. Rosario; P. Rule; C. Said; M. Sala-Rhatigan;
A. Stegmann; T. Stubblefield; K. Wiggins; J. Zimmerman
Submitted for publication November 1, 2013.
The method was approved by the Expert Review Panel for
Microbiology Methods for Feed and Environmental Surfaces as First
Action.
The Expert Review Panel for Microbiology Methods for Feed and
Environmental Surfaces invites method users to provide feedback on
the First Action methods. Feedback from method users will help verify
that the methods are fit for purpose and are critical to gaining global
recognition and acceptance of the methods. Comments can be sent
directly to the corresponding author or
1Corresponding author’s e-mail:
Supplemental data is available on the J. AOAC Int. website, http://
and follow link
to supplemental data.
DOI: 10.5740/jaoacint.13-372
FOOD BIOLOGICAL CONTAMINANTS
The VIDAS® UP Listeria (LPT) is an automated rapid
screening enzyme phage-ligand based assay for the
detection of Listeria species in human food products
and environmental samples. The VIDAS LPT method
was compared in a multi-laboratory collaborative
study to AOAC Official Method 993.12 Listeria
monocytogenes in Milk and Dairy Products reference
method following current AOAC guidelines. A
total of 14 laboratories participated, representing
government and industry, throughout the United
States. One matrix, queso fresco (soft Mexican
cheese), was analyzed using two different test
portion sizes, 25 and 125 g. Samples representing
each test portion size were artificially contaminated
with Listeria species at three levels, an uninoculated
control level [0 colony-forming units (CFU)/test
portion], a low-inoculum level (0.2–2 CFU/test
portion), and a high-inoculum level (2–5 CFU/test
portion). For this evaluation, 1800 unpaired replicate
test portions were analyzed by either the VIDAS
LPT or AOAC 993.12. Each inoculation level was
analyzed using the Probability of Detection (POD)
statistical model. For the low-level inoculated test
portions, difference in collaborator POD (dLPOD)
values of 0.01, (–0.10, 0.13), with 95% confidence
intervals, were obtained for both 25 and 125 g test
portions. The range of the confidence intervals
for dLPOD values for both the 25 and 125 g test
portions contains the point 0.0 indicating no
statistically significant difference in the number
of positive samples detected between the VIDAS
LPT and the AOAC methods. In addition to Oxford
agar, VIDAS LPT test portions were confirmed
using Agar Listeria Ottavani and Agosti (ALOA), a
proprietary chromogenic agar for the identification
and differentiation of L. monocytogenes and
Listeriaspecies. No differences were observed
between the two selective agars. The VIDAS LPT
method, with the optional ALOA agar confirmation
method, was adopted as Official First Action status
for the detection of Listeria species in a variety of
foods and environmental samples.
The current classification of the genus Listeria includes six
well-characterized species, with L. monocytogenes being
the species of most concern in foodborne outbreaks (1).
Listeria species are short, non-spore forming Gram-positive
rods that are ubiquitous in the environment and can be found in
soil, decaying vegetation, and most environments (2). While the
number of people who become ill from listeriosis, the disease
caused by Listeria, is relatively small, the high mortality rate
from infection makes it one of the leading causes of death
from foodborne illness (2). Of primary concern for illness from
Listeria outbreaks are the elderly, pregnant women, infants,
and people with compromised immune systems (3). Outbreaks
from Listeria have been linked to such foods as ready-to-eat
deli meats, hot dogs, pâtés, dairy products, soft cheeses, smoked
seafood, raw sprouts, and most recently cantaloupes (4). The
VIDAS UP Listeria (LPT) assay, an automated enzyme phage-
ligand based assay for the screening of Listeria in food and
environmental samples, provides the ability to detect Listeria
after only 26 h of enrichment.
TheVIDASLPTassay uses a primary enrichment (prewarmed
to 18–25°C) to detect Listeria species in 25 g test portions after
26–30 h of enrichment. For cantaloupe melons, whole melons
are soaked in approximately 1 L LPT broth and incubated
following conditions outlined for 25 g test portions. For larger
Candidates for 2016 Method of the Year
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